Although the present invention finds efficient uses in a wide range of biological, mechanical and electromechanical structures, for the purpose of efficient understanding hereof, this invention is discussed particularly as it pertains to biological fields such as in medicine and dentistry. In the dental industry, certain nonmetal dental prosthesis such as caps, crowns, pontics, etc., are manufactured from ceramic materials. Traditionally, the crowns or caps that are placed over prepared teeth are composed of an amorphous ceramic material that its built up by hand with powdered ceramic material and then fused in a high temperature oven either by one, two or three bakings at various temperatures to cause fusion of the silicon or glass materials. This is a very time consuming and painstaking process that requires a great deal of artistic skill on the part of the technician or ceramist. The requirement for a time consuming and painstaking process together with artistic skill of significant character greatly increases the cost of caps and crowns and other similar prosthesis. The technician or ceramist must be quite knowledgeable from the standpoint of color matching techniques in order to achieve development of a restoration of aesthetic quality. It is desirable therefore to provide an efficient method for manufacturing dental veneers, crowns, caps and other dental prosthesis which may be formed by a simplified manufacturing process and with a minimal of skilled labor and yet provide a resulting aesthetic restoration of optimum quality. It is also desirable to provide a preformed crown or cap structure which could be placed into an appropriate mold to form the crown or cap utilizing a fusion technique that would provide a tooth-like structure having the outward appearance of an aesthetic restoration without all the problems of color matching or technical training on the part of the technician involved in the manufacturing process. The cap or crown structure could be prefabricated to a general form and then molded to the precise shape and structural configuration of a prepared tooth in a controlled temperature furnace under either pressure or vacuum.
In the case of medical structures as prosthesis devices for replacement of bones and bone structure, ceramic materials are seldom employed because by nature such materials are generally of amorphous character and thereby lack energy absorbing capability that is necessary in bones. Moreover, bones have a microcellular or trabecular structure which renders them flexible and yet provides them with exceptional strength in both compression and tension. Heretofore, it has not been possible to provide medical prosthesis devices which have a cellular or trabecular structure and a strength-to-weight ratio which compares favorably with the structure of human bone. It is therefore desirable to provide a microcellular ceramic material having a microcellular structure which closely resembles the cellular trabecular structure of bone and which provides efficient bone-like strength-to-weight ratio as well as providing exceptional strength in compression, tension and bending.
Polymer materials such as polymethylmethacrylate and the like are typically employed in the manufacture of dental veneers. Such polymer materials, though finding wide acceptance, have a number of limiting factors that require improvement in order to render them acceptable for extended use in the oral environment. Although polymer materials may be colored for tooth-like appearance they typically lack the color depth and slight translucency of natural teeth. Further, the color systems of polymer dental veneers tend to degrade after extended use in the oral environment so that the veneers begin to lose their natural appearance. These materials also tend to reflect unusual color characteristics when exposed to certain wavelengths of light, thereby giving the teeth of the patient an unnatural color under some circumstances. Even more disadvantageous, polymer dental materials used for dental veneers tend to become stained and discolored after extended use especially where the patient smokes tobacco products, drinks tea and coffee or consumes certain food products having stains to which the polymers are susceptible. It is desirable therefore to provide dental laminate veneers and other dental prosthesis which resist staining, are more wear resistant than polymer veneers and which have permanent, nondegrading color systems that provide a normal tooth-like color and appearance.